Green beans are the young, unripe pods of the common bean, Phaseolus vulgaris, picked before the seeds inside swell and the pod turns tough. The same species gives kidney, black, pinto and navy beans, but those are eaten as dried seeds, while green beans are eaten as a vegetable. They are also called string beans, snap beans and French beans.
The name “string bean” comes from a tough string that once ran along the seam of the pod. Calvin Keeney, working in Le Roy, New York, bred the first stringless bean in 1894, and most modern varieties are stringless. Snap pods are picked about 8 to 10 days after flowering and break with an audible snap.
Green beans are light and low in calories: a cup (125 g) has 44 calories, 4 g of fiber and about 60 µg of vitamin K, half the daily value. Few trials have tested green beans on their own. Much of what is known comes from lab studies of what cooking, freezing and canning do to their vitamins, and those studies are the most useful part of the research below.
Health benefits of green beans
The top findings from 15 studies, strongest evidence first
What the stars mean
- Strong. Several randomized trials, pooled in a meta-analysis, point the same way, or regulators (FDA or EFSA) have approved the claim.
- Moderate. Good randomized trials support it, but there are fewer of them, or their results vary.
- Limited. Small, short or single trials, or mixed results. Promising, but it needs confirmation.
Population and lab studies get no stars: they show a link or a mechanism, not proof.
How we rate evidence →- ★Higher blood lutein from a vegetable mixIn healthy adults, 4 weeks of 180 g a day of green beans, pumpkin and sweet corn raised blood lutein by 37%. The vegetables were a mix, and macular pigment in the eye did not change.
- ★Infants accepted green beans more after varied vegetablesIn two experiments in 74 infants, 8 days of a variety of vegetables raised acceptance of green beans. Eating pears or varied fruits for 8 days did not carry over to green beans.
- ★Urine markers that track green bean intakeIn studies of 27 and 16 adults who ate green beans, 15 urine markers tracked intake. A panel of them sorted low from high intake with 91.6% accuracy, but it tracks what people eat, not health effects.
- ★Green bean allergy traced to one proteinIn 10 people with a confirmed green bean allergy, a lipid transfer protein called Pha v 3 was the major allergen. The authors say it is a risk for people with lipid transfer protein syndrome.
- Population studyLinked to lower stomach cancer riskIn a study in Jiangsu, China, of 187 people with stomach cancer and 333 controls, frequent snap bean eating went with lower risk. It relied on people recalling past diet.
All 15 studies, strongest evidence first
Eating 180 g a day of green beans, pumpkin and sweet corn for 4 weeks raised blood lutein in healthy adults
Trial in 29 healthy adults aged 45 to 65. A group of 15 ate 180 g a day of green beans, pumpkin and sweet corn, and 14 ate 500 g a day of oranges, kiwi and avocados, each giving 1.8 mg of lutein a day. Serum lutein rose 37%, and lutein plus zeaxanthin relative to HDL cholesterol rose more in the vegetable group. Macular pigment did not change. The vegetables were a mix, so green beans were not tested alone.
8 days of a variety of vegetables, both between and within meals, raised infants’ acceptance of green beans
Two experiments in 74 infants in total. In the second, vegetable variety also raised acceptance of carrots and spinach, and infants who had green beans alone between meals tended to eat more of them afterward. In the first, 8 days of pears or a variety of fruits raised pear intake but did not carry over to green beans. The abstract gives no intake figures.
Eating green beans left 15 urine markers that track how much a person ate
In an acute study, 27 adults ate green beans and gave urine samples before and after, and a follow-up of 16 people tested different portion sizes. A total of 745 NMR spectral regions and 318 mass spectrometry features rose after eating. A panel of the markers sorted low from high intake with 91.6% accuracy. It tracks what people eat, not health effects.
In 10 people with green bean allergy, a lipid transfer protein called Pha v 3 was the major allergen
Study of 10 Spanish patients who reported reactions to green beans, using skin prick tests, IgE tests and an oral challenge, which confirmed the allergy. A 10 kDa protein, identified as a non-specific lipid transfer protein, was recognized by 80% of their sera. The authors say it is a risk for people with lipid transfer protein syndrome. The study does not say how common green bean allergy is.
Frequent snap bean eating went with a lower risk of stomach cancer in a case-control study in Jiangsu, China
Study of 199 people with esophageal cancer, 187 with stomach cancer and 333 controls in a low-risk area. Frequent raw vegetables and garlic went with lower esophageal cancer risk. The abstract gives no size for the snap bean link, and case-control studies depend on people recalling past diet.
In a cooking test of 20 vegetables, green beans kept their antioxidant activity after most cooking methods
Lab test of boiling, microwaving, pressure cooking, griddling, frying and baking. Green bean values in the ABTS (TEAC) assay rose after every method except boiling. Across the vegetables, griddling, microwaving and baking lost the least and pressure cooking and boiling the most. These are tube assays of antioxidant chemistry, not effects in people.
Cooking frozen green beans in a boil-in-bag pouch kept 80.5% of the vitamin C, against 50.4% after boiling in water
Lab comparison using industrially blanched, frozen, tip-cut green beans. Total phenolics recovered were 89.2% against 76.7%. Conventional cooking let 13.5 to 42.8% of the nutrients leak into the cooking water, and sous vide matched the pouch. Warm-holding the beans after cooking lowered recoveries, and the authors suggest using the cooking liquid in the dish.
Boiling frozen green beans lost 18.2% of their vitamin C in a stainless steel pan and 42.1% in a pyrex pan
Lab test on frozen spinach, peas, green beans and okra boiled without thawing. Thawing first cost green beans 19.6% of their vitamin C, the most of the four vegetables, and boiling thawed beans in a pyrex pan lost 48.4%. The authors advise cooking frozen vegetables straight from the freezer in a minimum of water.
Boiled frozen green beans kept as many or more bioactive compounds as green beans boiled from raw
Lab study that followed asparagus, green beans and zucchini through blanching, freezing, storage and boiling, measuring chlorophylls, lutein, polyphenols and vitamin C. Blanching kept the phytochemicals, and frozen storage for up to 2 months did not lower lutein or flavonoids in almost all samples. Color changed, and the authors say well-made frozen vegetables are not lower in nutritional value.
Frozen green beans had beta-carotene comparable to fresh, and frozen produce overall matched fresh for most vitamins
Lab study at the University of California, Davis, of four vitamins in eight fruits and vegetables, including green beans, stored refrigerated or frozen and tested at three times. Ascorbic acid did not differ in five of the eight foods and was higher in frozen in the other three, while beta-carotene fell sharply in some frozen foods, such as peas, carrots and spinach. The abstract does not break out the other vitamins for green beans.
Canning green beans cut their folate by 30%, mostly by leaching into the covering liquid
Lab study that tracked folate along an industrial canning line for green beans. The drop came after sterilization, and 20% of the starting folate ended up in the covering liquid. The authors suggest less contact with water, or steaming, to limit losses during processing.
Cooking in water lowered the potassium in green bean pods and chard, a tool for people with kidney disease on low-potassium diets
Lab measurements on fresh, frozen and preserved vegetables, comparing soaking, double cooking and ordinary cooking. All methods cut potassium significantly, and frozen products lost more than fresh ones, in some cases over 90%. A single ordinary cooking often reached levels the authors call acceptable for kidney patients. The abstract gives no figures for green beans alone.
Extracts of boiled green pods blocked the carbohydrate-digesting enzyme α-glucosidase in a lab test
Test on four green pod samples from Chilean bean landraces. The phenolic content of the boiled pods was low, with rutin and quercetin 3-O-glucuronide as the main ones. This was an enzyme assay in a tube, not a blood sugar test in people.
About 90% of the fiber in green beans was fermented by gut bacteria in a rat model, whichever way the beans were processed
Lab and rat study of blanched and microwaved green beans. Repeated microwaving broke the water-soluble fiber into smaller pieces, but fermentability stayed high (about 90%) and similar across the processed beans. It did not test health effects.
Rats fed 25% freeze-dried green beans showed stronger liver changes after aflatoxin B1 than rats on a plain diet
Study in rats, not people, from 1983. Weanling rats ate diets with 25% freeze-dried green beans, beets or squash, with or without 1 ppm of aflatoxin B1, for 8 weeks. All three vegetables raised a blood marker and liver cell foci linked to aflatoxin-induced changes, and the authors suggest natural factors in these vegetables. The diet held a very large share of vegetable.
Who should be careful with green beans
Most people can eat green beans freely. Take a little care if one of these applies:
- Warfarin. A cup (125 g) has about 60 µg of vitamin K, which can change how this blood thinner works. A UK hospital leaflet lists green beans among vitamin K foods and advises a steady amount from week to week, not avoiding them, with a check with your clinic before big changes.
- Home-canned green beans. Green beans are a low-acid food, and home-canned vegetables are the most common cause of botulism outbreaks in the United States. Three outbreaks in 2008 and 2009 traced to home-canned vegetables, two of them involving green beans, where canners did not use pressure cookers. The CDC says to use a pressure canner for low-acid foods, not a boiling water canner.
- Eating them raw. Green beans contain a lectin, and Wikipedia says they should not be eaten raw. The official warnings (FDA, EFSA) are about raw or undercooked dried beans, especially red kidney beans, and none gives a level for green pods. The risk from a few raw beans is unknown, so cook them until tender.
How to choose, store and eat green beans
- Cooked, with little water: in a lab test of 20 vegetables, green beans kept their antioxidant activity after most cooking methods, and boiling and pressure cooking lost the most across the vegetables. Boil-in-bag cooking kept 80.5% of the vitamin C in frozen beans, against 50.4% when boiled in water.
- Frozen: frozen green beans had beta-carotene comparable to fresh in a University of California, Davis test, and boiled frozen beans kept as many or more bioactive compounds than boiled fresh ones. Cook them straight from the freezer: thawing first cost 19.6% of the vitamin C.
- Canned: canning cut folate by 30% in an industrial line, and 20% of it ended up in the liquid, so use the liquid in soup or a sauce. Raw is not recommended, for the reason above.
Choose smooth, bright green pods that are firm enough to snap when bent, and keep them unwashed in a plastic bag in the fridge for up to a week. Residues are worth a calm word: in USDA tests of 530 green bean samples in 2022, 38 had a residue above the legal limit, against about 0.5% of all foods tested, while USDA says the residues it finds are at levels that do not pose a risk to health, according to EPA and FDA.
Sources
- Dietary advice for patients taking warfarin. Cambridge University Hospitals NHS Foundation Trust.
- Anticoagulant medicines: considerations. NHS.
- Date K, Fagan R, Crossland S, et al. Three outbreaks of foodborne botulism caused by unsafe home canning of vegetables, Ohio and Washington, 2008 and 2009. J Food Prot. 2011.
- Botulism: information for consumers, home canning. CDC.
- Lectins in food: undercooked beans pose health risk, says EFSA. European Food Safety Authority. 2026.
- Bad Bug Book, second edition: phytohaemagglutinin (kidney bean lectin). US Food and Drug Administration.
- Green bean. Wikipedia.
- Green beans. University of Nebraska–Lincoln Extension.
- Jiménez-Monreal AM, García-Diz L, Martínez-Tomé M, Mariscal M, Murcia MA. Influence of cooking methods on antioxidant activity of vegetables. J Food Sci. 2009.
- Baardseth P, Bjerke F, Martinsen BK, Skrede G. Vitamin C, total phenolics and antioxidative activity in tip-cut green beans (Phaseolus vulgaris) and swede rods (Brassica napus var. napobrassica) processed by methods used in catering. J Sci Food Agric. 2010.
- Nursal B, Yücecan S. Vitamin C losses in some frozen vegetables due to various cooking methods. Nahrung. 2000.
- Mazzeo T, Paciulli M, Chiavaro E, et al. Impact of the industrial freezing process on selected vegetables, Part II. Colour and bioactive compounds. Food Res Int. 2015.
- Bouzari A, Holstege D, Barrett DM. Vitamin retention in eight fruits and vegetables: a comparison of refrigerated and frozen storage. J Agric Food Chem. 2015.
- Delchier N, Ringling C, Le Grandois J, et al. Effects of industrial processing on folate content in green vegetables. Food Chem. 2013.
- Getting enough fibre: low FODMAP foods and IBS. Monash FODMAP blog.
- Pesticide Data Program annual summary, calendar year 2022. USDA Agricultural Marketing Service.
History of green beans
The green bean starts in the Americas. Wild common beans are native there, and they were domesticated separately in Mesoamerica and the southern Andes about 8,000 years ago, giving two gene pools. A genetic study of 214 wild and domesticated plants found a single domestication event in each pool, and points to the Oaxaca valley in Mexico and to southern Bolivia and northern Argentina as the likely origins.
Common beans reached Europe in the 16th century through the Columbian exchange. In 1528, according to Wikipedia, Pope Clement VII received white beans that thrived there. Beans grown in Europe before then were of Asian origin and unrelated to the New World Phaseolus species.
Early pods had a tough string along the seam that cooks had to pull off. Calvin Keeney, working in Le Roy, New York, bred the first stringless bean in 1894, and he is called the father of the stringless bean. Snap pods are harvested about 8 to 10 days after flowering, while they are still tender.
The best-known green bean dish is American. Dorcas Reilly, who worked in the home economics department at the Campbell Soup Company in Camden, New Jersey, developed the green bean casserole in 1955 for an Associated Press feature that asked for a quick dish made from common ingredients. It was first called “Green Bean Bake” and tested poorly inside the company at first. Campbell’s estimated in 2020 that it was served at 20 million US Thanksgiving dinners a year.
Today most green beans are grown in China. FAO figures cited by Wikipedia put world production at 25.9 million tonnes in 2024, with 18.6 million tonnes, about 72%, from China, followed by India at 2.9 million tonnes.
Sources
- Bitocchi E, Bellucci E, Giardini A, et al. Molecular analysis of the parallel domestication of the common bean (Phaseolus vulgaris) in Mesoamerica and the Andes. New Phytol. 2013.
- Common bean. Wikipedia.
- Green bean. Wikipedia.
- Green bean casserole. Wikipedia.
Frequently asked questions about green beans
Are green beans good for you?
For most people, yes. Raw green beans have 35 calories, 1.9 g of protein and 3.2 g of fiber per 100 g, and a cup (125 g) covers half the daily value of vitamin K and about a tenth of the vitamin C. Few trials have tested them, though: the best human result here is a small 4-week trial where a mix of green beans, pumpkin and sweet corn raised blood lutein.
Can you eat green beans raw?
It is not recommended. Green beans contain a lectin, a protein that is toxic in raw or undercooked beans, and the FDA says it is found in many species of beans, highest in red kidney beans. No source here measured it in green pods, so the risk from a few raw beans is unknown. Cooking them until tender is the safe choice.
Are green beans a legume or a vegetable?
Both. They are the unripe pods of a legume plant, Phaseolus vulgaris, and they are eaten as a vegetable. Dried beans are eaten as seeds with far more protein and calories, so research on dried beans and pulses does not apply to green beans.
What is the healthiest way to cook green beans?
Cook them briefly in little water. In a lab test of 20 vegetables, green beans kept their antioxidant activity after most cooking methods, and boiling and pressure cooking lost the most across the vegetables. Boil-in-bag cooking kept 80.5% of the vitamin C in frozen beans, against 50.4% when boiled in water, and the authors suggest using the cooking liquid in the dish.
Are frozen or canned green beans as healthy as fresh?
Frozen ones are close to fresh. Frozen green beans had beta-carotene comparable to fresh, and boiled frozen beans kept as many or more bioactive compounds than boiled fresh ones. Canning is different: it cut folate by 30%, with 20% moving into the covering liquid. Cook frozen beans without thawing, since thawing first cost 19.6% of the vitamin C.
Are green beans high in protein?
Not high, but they add some. A cup (125 g) has 2.4 g of protein, or 1.9 g per 100 g, about 22% of its calories. Its protein completeness score is 87 out of 100, with methionine and cysteine the limiting amino acids.
Can you eat green beans on warfarin?
Yes, in a steady amount. A cup (125 g) of green beans has about 60 µg of vitamin K, half the daily value, and a UK hospital leaflet lists them among vitamin K foods. It advises keeping the amount the same from week to week and checking with your clinic before big changes.
Do green beans cause gas?
They can in some people, and no trial here measured it. Monash University lists 15 green beans (75 g) among the portions that fit a low FODMAP serve. If beans bother you, start with a small portion.